RETURNS TO SCALE: Changes in production the occurs when all resources are proportionately increased in the long run. Returns to scale answers the question: If labor, capital, and ALL other inputs increase by 10%, does output increase by more than 10%, less than 10%, or exactly 10%? These answers indicate that returns to scale can take one of three forms: increasing returns to scale, decreasing returns to scale, and constant returns to scale.

NASH EQUILIBRIUM: A concept from Game Theory which establishes that a set of strategies followed by economic agents within a game is in equilibrium if, holding the strategies of all other economic agents constant, no economic agent can obtain a higher payoff by choosing a different strategy. For example, when firms operate within an oligopoly, once a Nash equilibrium has been reached, none of them will want to change their strategy because by doing it they cannot obtain a higher profit.

Total cost per unit of output, found by dividing total cost by the quantity of output. When compared with price (per unit revenue), average total cost (ATC) indicates the per unit profitability of a profit-maximizing firm. Average total cost is one of three average cost concepts important to short-run production analysis. The other two are average fixed cost and average variable cost. A related concept is marginal cost.

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